Sign suspension system

Abstract

A remote-controlled motor-driven drum is provided to wind and unwind a cord which holds a self-balancing sign carrier. The sign carrier, which has telescoping rails, is adjustable in width. Its center rail includes two sheaves to receive the cord and lead it from the drum back to an end secured to the ceiling. Rotation of the drum raises and lowers the sign carrier and a sign carried by it. The sheaves on the carrier also serve to make the unit self-balancing. The motor responds to actuating signals for raising and lowering the sign and to safety features. Safety features include a limit switch which stops the motor when an object gets in the way, an overload control which stops the motor if excessive weight is detected, and the use of the motor for braking.

What is claimed is:  
     
       1. A system for suspending a sign, comprising: 
       a member for supporting said sign;  
       a cord supporting said member;  
       a motor unit having a reversible motor and a drum operated by said reversible motor, said motor unit engaging said cord such that said cord is wound around said drum for raising and lowering said sign;  
       a switch, coupled to said motor unit, for providing first output control signals when an object contacts said switch;  
       a motor control unit, coupled to said reversible motor, for controlling bi-directional rotation of said reversible motor, said motor control unit comprising:  
       a detector, responsive to received actuating signals, for providing second output control signals;  
       a sensor for detecting an overload condition on the reversible motor and for providing third output control signals;  
       a forward-reverse relay;  
       an on-brake relay; and  
       a microprocessor, coupled to said switch, said detector, said sensor, said forward-reverse relay and said on-brake relay, said microprocessor receives said first, second and third output control signals and activates said forward-reverse and said on-brake relays to control said bi-directional rotation of said reversible motor; and  
       a signal generating transmitter, physically separated from said motor control unit, for transmitting said actuating signals to said detector;  
       wherein in response to said first output control signals, said motor control unit controls said reversible motor to reverse a first direction and operate in a second direction reversed to said first direction for a predetermined time period before stopping;  
       wherein in response to said second output control signals, said motor control unit controls said reversible motor to operate in one of said first direction, said second direction and to terminate vertical motion of said sign;  
       wherein in response to said third output control signals, said motor control unit controls said reversible motor to terminate vertical motion of said sign.  
     
     
       2. The system as claimed in  claim 1  wherein said on-brake relay operates to stop said reversible motor by electronically shorting terminals of said reversible motor causing said reversible motor to brake and increase holding power when stopped. 
     
     
       3. The system as claimed in  claim 1  further comprising: 
       a plurality of motor units each at different locations; and  
       a plurality of signs; wherein  
       each of the signs mounts a corresponding motor unit.  
     
     
       4. The system as claimed in  claim 1  wherein the sensor includes means for determining the magnitude of a load that triggers said overload condition. 
     
     
       5. The system as claimed in  claim 1  wherein the detector is an infra red detector. 
     
     
       6. The system as claimed in  claim 5  wherein the infra red detector is responsive to signals received within a predetermined field of reception. 
     
     
       7. The system as claimed in  claim 1  wherein the signal generating transmitter generates and transmits infra red actuating signals. 
     
     
       8. The system as claimed in  claim 1  further comprising: 
       a reduction gear connecting the reversible motor to the drum.  
     
     
       9. The system as claimed in  claim 1  wherein said predetermined time period comprises a time period of about 600 ms. 
     
     
       10. The system as claimed in  claim 1  wherein said predetermined time period comprises a time period for operating said reversible motor in said reversed direction such that said sign travels a predetermined safe distance from said object. 
     
     
       11. The system as claimed in  claim 10  wherein said predetermined safe distance is about one foot.